Thin disc, thick disc and halo in a simulated galaxy

C. B. Brook, G. S. Stinson, B. K. Gibson, D. Kawata, E. L. House, M. S. Miranda, Andrea Maccio, K. Pilkington, R. Roŝkar, J. Wadsley, T. R. Quinn

    Research output: Chapter in Book/Report/Conference proceedingChapter

    Abstract

    Within a cosmological hydrodynamical simulation, we form a disc galaxy with subcomponents which can be assigned to a thin stellar disc, thick disc and a low-mass stellar halo via a chemical decomposition. The thin- and thick-disc populations so selected are distinct in their ages, kinematics and metallicities. Thin-disc stars are young (<6.6 Gyr), possess low velocity dispersion (ωU, V, W =41, 31, 25 km s-1), high [Fe/H] and low [O/Fe]. Conversely, the thick-disc stars are old (6.6 < age < 9.8 Gyr), lag the thin disc by ~21 km s-1, possess higher velocity dispersion (sU, V, W = 49, 44, 35 km s-1) and have relatively low [Fe/H] and high [O/Fe]. The halo component comprises less than 4 per cent of stars in the 'solar annulus' of the simulation, has low metallicity, a velocity ellipsoid defined by sU, V, W = 62, 46, 45 km s-1 and is formed primarily in situ during an early merger epoch. Gas-rich mergers during this epoch play a major role in fuelling the formation of the old-disc stars (the thick disc). We demonstrate that this is consistent with studies which show that cold accretion is the main source of a disc galaxy's baryons. Our simulation initially forms a relatively short (scalelength ~1.7 kpc at z = 1) and kinematically hot disc, primarily from gas accreted during the galaxy's merger epoch. Far from being a competing formation scenario, we show that migration is crucial for reconciling the short, hot, discs which form at high redshift in cold dark matter, with the properties of the thick disc at z = 0. The thick disc, as defined by its abundances, maintains its relatively short scalelength at z = 0 (2.31 kpc) compared with the total disc scalelength of 2.73 kpc. The inside-out nature of disc growth is imprinted in the evolution of abundances such that the metal-poor a-young population has a larger scalelength (4.07 kpc) than the more chemically evolved metal-rich a-young population (2.74 kpc).

    Original languageEnglish (US)
    Title of host publicationRelativity in Fundamental Astronomy
    Subtitle of host publicationDynamics, Reference Frames, and Data Analysis
    Pages690-700
    Number of pages11
    EditionS261
    StatePublished - Apr 1 2009

    Publication series

    NameProceedings of the International Astronomical Union
    NumberS261
    Volume5
    ISSN (Print)1743-9213
    ISSN (Electronic)1743-9221

    Fingerprint

    halos
    galaxies
    stars
    disk galaxies
    time measurement
    metallicity
    refueling
    simulation
    annuli
    ellipsoids
    gases
    metals
    low speed
    baryons
    dark matter
    time lag
    kinematics
    decomposition

    Keywords

    • Disc-Galaxy
    • Evolution-galaxies
    • Evolution-Galaxy
    • Formation
    • Formation-galaxies
    • Galaxy

    ASJC Scopus subject areas

    • Astronomy and Astrophysics

    Cite this

    Brook, C. B., Stinson, G. S., Gibson, B. K., Kawata, D., House, E. L., Miranda, M. S., ... Quinn, T. R. (2009). Thin disc, thick disc and halo in a simulated galaxy. In Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis (S261 ed., pp. 690-700). (Proceedings of the International Astronomical Union; Vol. 5, No. S261).

    Thin disc, thick disc and halo in a simulated galaxy. / Brook, C. B.; Stinson, G. S.; Gibson, B. K.; Kawata, D.; House, E. L.; Miranda, M. S.; Maccio, Andrea; Pilkington, K.; Roŝkar, R.; Wadsley, J.; Quinn, T. R.

    Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis. S261. ed. 2009. p. 690-700 (Proceedings of the International Astronomical Union; Vol. 5, No. S261).

    Research output: Chapter in Book/Report/Conference proceedingChapter

    Brook, CB, Stinson, GS, Gibson, BK, Kawata, D, House, EL, Miranda, MS, Maccio, A, Pilkington, K, Roŝkar, R, Wadsley, J & Quinn, TR 2009, Thin disc, thick disc and halo in a simulated galaxy. in Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis. S261 edn, Proceedings of the International Astronomical Union, no. S261, vol. 5, pp. 690-700.
    Brook CB, Stinson GS, Gibson BK, Kawata D, House EL, Miranda MS et al. Thin disc, thick disc and halo in a simulated galaxy. In Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis. S261 ed. 2009. p. 690-700. (Proceedings of the International Astronomical Union; S261).
    Brook, C. B. ; Stinson, G. S. ; Gibson, B. K. ; Kawata, D. ; House, E. L. ; Miranda, M. S. ; Maccio, Andrea ; Pilkington, K. ; Roŝkar, R. ; Wadsley, J. ; Quinn, T. R. / Thin disc, thick disc and halo in a simulated galaxy. Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis. S261. ed. 2009. pp. 690-700 (Proceedings of the International Astronomical Union; S261).
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    abstract = "Within a cosmological hydrodynamical simulation, we form a disc galaxy with subcomponents which can be assigned to a thin stellar disc, thick disc and a low-mass stellar halo via a chemical decomposition. The thin- and thick-disc populations so selected are distinct in their ages, kinematics and metallicities. Thin-disc stars are young (<6.6 Gyr), possess low velocity dispersion (ωU, V, W =41, 31, 25 km s-1), high [Fe/H] and low [O/Fe]. Conversely, the thick-disc stars are old (6.6 < age < 9.8 Gyr), lag the thin disc by ~21 km s-1, possess higher velocity dispersion (sU, V, W = 49, 44, 35 km s-1) and have relatively low [Fe/H] and high [O/Fe]. The halo component comprises less than 4 per cent of stars in the 'solar annulus' of the simulation, has low metallicity, a velocity ellipsoid defined by sU, V, W = 62, 46, 45 km s-1 and is formed primarily in situ during an early merger epoch. Gas-rich mergers during this epoch play a major role in fuelling the formation of the old-disc stars (the thick disc). We demonstrate that this is consistent with studies which show that cold accretion is the main source of a disc galaxy's baryons. Our simulation initially forms a relatively short (scalelength ~1.7 kpc at z = 1) and kinematically hot disc, primarily from gas accreted during the galaxy's merger epoch. Far from being a competing formation scenario, we show that migration is crucial for reconciling the short, hot, discs which form at high redshift in cold dark matter, with the properties of the thick disc at z = 0. The thick disc, as defined by its abundances, maintains its relatively short scalelength at z = 0 (2.31 kpc) compared with the total disc scalelength of 2.73 kpc. The inside-out nature of disc growth is imprinted in the evolution of abundances such that the metal-poor a-young population has a larger scalelength (4.07 kpc) than the more chemically evolved metal-rich a-young population (2.74 kpc).",
    keywords = "Disc-Galaxy, Evolution-galaxies, Evolution-Galaxy, Formation, Formation-galaxies, Galaxy",
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    AU - Stinson, G. S.

    AU - Gibson, B. K.

    AU - Kawata, D.

    AU - House, E. L.

    AU - Miranda, M. S.

    AU - Maccio, Andrea

    AU - Pilkington, K.

    AU - Roŝkar, R.

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    AU - Quinn, T. R.

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    N2 - Within a cosmological hydrodynamical simulation, we form a disc galaxy with subcomponents which can be assigned to a thin stellar disc, thick disc and a low-mass stellar halo via a chemical decomposition. The thin- and thick-disc populations so selected are distinct in their ages, kinematics and metallicities. Thin-disc stars are young (<6.6 Gyr), possess low velocity dispersion (ωU, V, W =41, 31, 25 km s-1), high [Fe/H] and low [O/Fe]. Conversely, the thick-disc stars are old (6.6 < age < 9.8 Gyr), lag the thin disc by ~21 km s-1, possess higher velocity dispersion (sU, V, W = 49, 44, 35 km s-1) and have relatively low [Fe/H] and high [O/Fe]. The halo component comprises less than 4 per cent of stars in the 'solar annulus' of the simulation, has low metallicity, a velocity ellipsoid defined by sU, V, W = 62, 46, 45 km s-1 and is formed primarily in situ during an early merger epoch. Gas-rich mergers during this epoch play a major role in fuelling the formation of the old-disc stars (the thick disc). We demonstrate that this is consistent with studies which show that cold accretion is the main source of a disc galaxy's baryons. Our simulation initially forms a relatively short (scalelength ~1.7 kpc at z = 1) and kinematically hot disc, primarily from gas accreted during the galaxy's merger epoch. Far from being a competing formation scenario, we show that migration is crucial for reconciling the short, hot, discs which form at high redshift in cold dark matter, with the properties of the thick disc at z = 0. The thick disc, as defined by its abundances, maintains its relatively short scalelength at z = 0 (2.31 kpc) compared with the total disc scalelength of 2.73 kpc. The inside-out nature of disc growth is imprinted in the evolution of abundances such that the metal-poor a-young population has a larger scalelength (4.07 kpc) than the more chemically evolved metal-rich a-young population (2.74 kpc).

    AB - Within a cosmological hydrodynamical simulation, we form a disc galaxy with subcomponents which can be assigned to a thin stellar disc, thick disc and a low-mass stellar halo via a chemical decomposition. The thin- and thick-disc populations so selected are distinct in their ages, kinematics and metallicities. Thin-disc stars are young (<6.6 Gyr), possess low velocity dispersion (ωU, V, W =41, 31, 25 km s-1), high [Fe/H] and low [O/Fe]. Conversely, the thick-disc stars are old (6.6 < age < 9.8 Gyr), lag the thin disc by ~21 km s-1, possess higher velocity dispersion (sU, V, W = 49, 44, 35 km s-1) and have relatively low [Fe/H] and high [O/Fe]. The halo component comprises less than 4 per cent of stars in the 'solar annulus' of the simulation, has low metallicity, a velocity ellipsoid defined by sU, V, W = 62, 46, 45 km s-1 and is formed primarily in situ during an early merger epoch. Gas-rich mergers during this epoch play a major role in fuelling the formation of the old-disc stars (the thick disc). We demonstrate that this is consistent with studies which show that cold accretion is the main source of a disc galaxy's baryons. Our simulation initially forms a relatively short (scalelength ~1.7 kpc at z = 1) and kinematically hot disc, primarily from gas accreted during the galaxy's merger epoch. Far from being a competing formation scenario, we show that migration is crucial for reconciling the short, hot, discs which form at high redshift in cold dark matter, with the properties of the thick disc at z = 0. The thick disc, as defined by its abundances, maintains its relatively short scalelength at z = 0 (2.31 kpc) compared with the total disc scalelength of 2.73 kpc. The inside-out nature of disc growth is imprinted in the evolution of abundances such that the metal-poor a-young population has a larger scalelength (4.07 kpc) than the more chemically evolved metal-rich a-young population (2.74 kpc).

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